High-purity perfluoro-4-methyl-2-pentene and its preparation and use

Abstract

The toxic perfluoro-2-methyl-2-pentene can be removed from perfluoro-4-methyl-2-pentene by treating the mixture with lower alkanols, the toxic isomer being converted into high boiling-point compounds which can be easily removed. The high-purity perfluoro-4-methyl-2-pentene so obtained is suitable as a substitute for chlorofluorocarbons.

What is claimed is: 
     
       1. A process for preparing a perfluoro-4-methyl-2-pentene having a content of perfluoro-2-methyl-2-pentene of below 1000 ppm, which comprises: treating a starting material comprising a major amount of perfluoro-4-methyl-2-pentene and a minor amount of perfluoro-2-methyl-2-pentene, said minor amount being greater than 1000 ppm, with a lower alkanol and a catalytic amount of a base, and removing any compound or compounds, higher boiling than perfluoro-2-methyl-2-pentene, formed from said perfluoro-2-methyl-2-pentene as a result of said treatment.   
     
     
       2. The process as claimed in claim 1, wherein the amount of lower alcohol is stoichiometrically in excess with respect to said minor amount of perfluoro-2-methyl-2-pentene. 
     
     
       3. The process as claimed in claim 1, wherein the said lower alkanol has from 1 to 3 carbon atoms. 
     
     
       4. The process as claimed in claim 1, wherein the treatment with the lower alkanol is carried out at a temperature of from 0° to 35° C. 
     
     
       5. The process as claimed in claim 1, wherein the base is a tertiary amine. 
     
     
       6. The process as claimed in claim 1, wherein the treatment is carried out over a period of up to 3 hours. 
     
     
       7. The process as claimed in claim 1, comprising: mixing said starting material with said lower alkanol in the presence of said base, thereby forming a mixture having a plurality of liquid phases,   providing intimate contact between said liquid phases until the perfluoro-2-methyl-2-pentene is substantially converted into a compound having a higher boiling point than perfluoro-2-methyl-2-pentene, and   separating the perfluoro-4-methyl-2-pentene from said lower alkanol and a said compound having a higher boiling point, thereby recovering perfluoro-4-methyl-2-pentene having a content of less than 1000 ppm of perfluoro-2-methyl-2-pentene.